1. Field of the Invention
The invention relates to substrate handling systems, and more particularly, to systems for loading and unloading substrates into and from a processing environment.
2. Description of Related Art
Substrates such as semiconductor wafers are conventionally handled in protective containers which seal out contaminants prior to commencement of processing procedures. The processing procedures themselves are performed in a micro environment system having one or more processing stations into and out of which the wafers are transferred from the protective containers. The conditions in the micro environment system are carefully managed such that temperature and humidity are controlled, and use is made of air filtration systems which remove contaminants that would otherwise corrupt the delicate manufacturing procedures involved. Complex systems are used to effect these controls, and expedients used include establishing laminar flows within the micro environment to direct air flow towards the filtration devices.
Typically, a storage container comprises a pod containing a plurality of semiconductor wafers stacked in a cassette. When ready for processing, the pod containing the wafers is docked with an interface chamber, referred to as a load lock chamber, of the micro environment. The load lock chamber is provided with a port having a door supported therein. The door, normally closed to preserve the micro environment conditions, is opened when the pod is in the docked position. A door of the pod is also opened, thereby permitting transport of the semiconductor wafers between the pod and the micro environment through the load lock chamber.
Opening and closing of the pod and load lock chamber doors is automated. An opening mechanism provided in the load lock chamber simultaneously engages both doors, often sealing them together to sandwich contaminants therebetween, and removes them along a transport path to a remote position to thereby facilitate transfer of the wafers, by a different loading and unloading mechanism, between the pod and the load lock chamber. Prior art devices of this type include U.S. Pat. No. 5,607,276 to Muka, et al., U.S. Pat. No. 5,609,459 to Muka, U.S. Pat. No. 5,613,821 to Muka, et al., and U.S. Pat. No. 5,664,925 to Muka, et al.
Disadvantages attendant to the aforementioned prior art systems include the additional expense of the opening mechanism and the establishment of large exclusion zones which the opening mechanism and the transport path of the doors must necessarily occupy. Moreover, the complexity of the opening mechanism adds to operational expenses and increases the likelihood of system malfunction. Additionally, operation of the opening mechanism must be appropriately controlled and synchronized to the system as a whole, further complicating system operation and burdening system resources.